How to Temper Eggs
Quick steps (15 min)
You need: saucepan, mixing bowl, whisk, ladle, heatproof spatula, fine-mesh sieve, instant-read thermometer
To temper eggs, you whisk a small amount of hot liquid into beaten eggs or yolks to warm them slowly, then pour the warmed eggs back into the hot liquid and cook gently. This keeps the eggs smooth so they thicken the mixture instead of scrambling.
Why eggs curdle
Egg yolk proteins start to set around 65 °C / 149 °F. Pour cold yolks straight into a pot of steaming milk and the yolk that touches the liquid first jumps past that point instantly, setting into tiny lumps before it can disperse.
Tempering solves two problems at once. Adding hot liquid a little at a time raises the eggs' temperature gradually. It also dilutes them, spreading the proteins out so they meet each other less often. Diluted, sweetened egg proteins don't set firm until much higher temperatures.
How sugar and dilution protect eggs
On its own, beaten egg sets well below 80 °C / 176 °F. Mixed with milk, cream and sugar, the same egg can be heated to 77–82 °C / 170–180 °F before it thickens, and it doesn't curdle until roughly 85 °C / 185 °F.
Sugar molecules get between the proteins and slow their bonding. Fat from cream does something similar. That is why recipes have you whisk sugar into the yolks before tempering: it builds in a safety margin.
The target: nappe
A properly cooked stirred custard such as crème anglaise reaches 77–82 °C / 170–180 °F. At that point it coats a spoon in a smooth, even layer, and a finger swiped across the back of the spoon leaves a clean line. Cooks call this stage nappe. It also takes the eggs past 71 °C / 160 °F, the temperature that makes them safe.
A thermometer removes the guesswork. Stirred custards go from nappe to curdled within just a few degrees.
Starch changes the rules
Pastry cream, pudding and some pie fillings contain flour or cornstarch. Starch granules swell and get between the egg proteins, so these mixtures can be brought to a full boil without curdling. In fact they should boil for about a minute. Raw yolks contain an enzyme called amylase that breaks down starch; if you don't heat it out, the pastry cream turns runny overnight.
You still temper eggs for pastry cream, but you then whisk it over medium heat until it bubbles.
Steps
- Heat the milk or cream until steaming, about 80 °C / 175 °F. Small bubbles should form at the edge of the pan. It doesn't need to boil.
- Whisk the yolks and sugar in a bowl until smooth and slightly pale. About 30 seconds of whisking dissolves the sugar into the yolks. Don't leave yolks sitting with sugar on top; sugar draws water out of the yolk and leaves hard, grainy specks.
- Set the bowl on a damp towel so it won't spin. You need one hand for the whisk and one for the ladle.
- Pour a ladle of hot liquid into the yolks in a thin stream, whisking constantly. About 125 mL (1/2 cup) at a time is right for a standard 500 mL custard.
- Add a second ladle the same way. Once about a third of the hot liquid is in, the eggs are warm and diluted enough to go back to the pot.
- Pour the warmed yolk mixture back into the pot. Whisk the pot as you pour.
- Cook over low heat, stirring, until it reaches 77–82 °C / 170–180 °F. Use a heatproof spatula and scrape the bottom and corners constantly; this takes 3 to 6 minutes. For pastry cream, switch to a whisk and bring it to a boil for 1 minute.
- Strain immediately into a clean bowl and cool. The pot's heat keeps cooking the custard, so move it out quickly. Press plastic wrap onto the surface to stop a skin forming, then chill.
Common mistakes and fixes
- Lumps of scrambled egg. The liquid went in too fast or wasn't whisked in. Strain the mixture and carry on if it's only a few bits.
- Custard starting to look grainy. It's just above temperature. Pull the pan off the heat, pour into a cold bowl set over ice and blend with an immersion blender. This often rescues it.
- Custard never thickens. It didn't get hot enough. Keep cooking on low until it reaches 77 °C / 170 °F.
- Scorched bottom. The heat was too high or the bottom wasn't scraped. Use a heavy pan and low heat.
- Pastry cream turned runny overnight. It didn't boil long enough to switch off the yolk amylase. Boil a full minute next time.
Where you'll use it
Tempering is the base of crème anglaise, ice cream custard, pastry cream, lemon curd, eggnog, avgolemono soup and egg-yolk liaisons for sauces. The method is the same each time; only the final temperature changes.
Questions
What does it mean to temper eggs?
Tempering means warming eggs gradually by whisking in small amounts of hot liquid before combining everything. It raises the eggs' temperature slowly and dilutes them, so they thicken a sauce instead of turning into scrambled bits.
How do you know when tempered custard is done?
It reaches 77–82 °C / 170–180 °F and coats the back of a spoon; a finger drawn through the coating leaves a clean line that holds. This stage is called nappe.
Can you fix curdled custard?
If it has only just started to curdle, strain it at once into a cold bowl and blend with an immersion blender. Heavily curdled custard with large lumps can't be fully rescued.
Why can pastry cream boil but crème anglaise can't?
Pastry cream contains starch, which surrounds the egg proteins and stops them from clumping, so it can boil safely. It actually needs a brief boil to switch off an enzyme in yolks that would otherwise thin the starch.
Do you need to temper eggs for every recipe?
Only when eggs meet hot liquid, such as custards, pastry cream, ice cream bases, lemon curd, carbonara-style sauces and egg-thickened soups. Eggs going into a cold batter don't need tempering.